4. Reluctance to walk, arched back and tucked up abdomen 5. Scant, hard faeces, rarely covered with mucus. 6. Mild rumen bloat 7. Audible “grunt” in early stages If mild septicemia develops the animal shows: 8. Elevated temperature (39.2 ° C - 40° C) 9. Increased heart rate In chronic localized peritonitis, acute signs and pain lessen, temperature falls and stomach reticulo-rumen motility may return. Postmortem findings : 1. Adhesions of rumen, reticulum and peritoneum and abscessation 2. Acute or chronic peritonitis 3. Splenic abscessation 4. Traumatic pericarditis (Fig. 85) 5. Metallic objects such as nails, pieces of wire, magnets etc. in the reticulum 6. Lung abscessation or pneumonia 7. Septic pleuritis 8. Edema of the chest Judgement : Viscera and carcass are condemned - a) if the animal is affected with acute diffuse peritonitis or acute infectious pericarditis associated with septicemia; b) carcass with traumatic pericarditis associated with fever, large accumulation of exudate, circulatory disturbances, degenerative changes in organs, or abnormal odour. c) carcass with chronic traumatic reticulo-peritonitis and/or purulent pericarditis with associated pleuritis, abscessation and edema of the chest. Chronic adhesive localized peritonitis and chronic pericarditis without systemic changes in well nourished animals allow a favourable judgement of the carcass. The affected parts of the carcass and organs are condemned. A carcass affected with infectious exudative pericarditis in a subacute stage may be conditionally approved pending heat treatment, if bacteriological and antibiotic residue findings are negative. Differential diagnosis : Uterine or vaginal trauma, abomasal ulceration with perforation, liver abscessation, pyelonephritis, ketosis, abomasal displacement and volvulus, and “grain overload”. 121 Fig. 85: TRP. Cross section of the heart reveals thick fibrinous deposits that encircled heart. Rusty nail has penetrated through the wall of the reticulum into the pericardium in this case. 122 CHAPTER 4 SPECIFIC DISEASES OF PIGS Diseases caused by viruses African Swine Fever (ASF) ASF is a highly contagious viral disease of domestic pigs manifested by fever, blotching of skin, haemorrhage of the lymph nodes, internal organs and haemorrhage of the gastrointestinal tract. It is observed in acute and occasionally subacute and chronic forms. Transmission : There is a natural cycle of the ASF virus between bush pigs, warthogs and giant forest hogs and some tick species (Ornithodorus) in which the virus replicates. The spread of the virus is by contact with affected pigs and infected fomites, ingestion of contaminated uncooked pork garbage, tick bites and contact with domestic and wild carrier pigs. The virus is quite resistant to cleaning and disinfection. It survives for 2 – 4 months in an infected premises and 5 – 6 months in infected meats. The virus can survive in smoked or partly cooked sausages and other pork products. Humans are not susceptible to this disease. Antemortem findings : 1. Incubation: 3 – 15 days 2. Fever (up to 42°C) 3. Laboured breathing, coughing 4. Nasal and ocular discharge 5. Loss of appetite and diarrhoea 6. Vomiting 7. Incoordination 8. Cyanosis of the extremities and haemorrhages of skin 9. In chronic stage, emaciation and edematous swelling under the mandible and over leg joints 10. Recumbency Postmortem findings : 1. Blotchy skin cyanosis and haemorrhage (Fig. 113) 2. Enlarged spleen (splenomegaly, Fig 114) 3. Petechial haemorrhage on the kidneys (Fig. 115) 4. Enlarged and haemorrhagic gastrohepatic and renal lymph nodes 5. Haemorrhage in the heart 6. Hydrothorax, hydropericardium and ascites 123 7. Haemorrhage of the serous membranes 8. In chronic ASF pericarditis, and emaciated carcass Judgement : Carcass of an animal affected with African Swine Fever is condemned. The animal is prohibited from entering the abattoir. Differential diagnosis : Hog cholera, salmonellosis, erysipelas, Glasser's disease (Haemophilus suis) infection Fig. 113: African swine fever. Blotchy skin, cyanosis and haemorrhage. Fig. 114: African swine fever. Enlarged spleen (splenomegaly). 124 Fig. 115: African swine fever. Petechial and ecchymotic haemorrhage in the kidneys. Note haemorrhagic areas in the renal pelvis and papillae. Foot and Mouth Disease (FMD, Aphthous fever) FMD is a contagious, viral disease of swine, cattle, sheep, goats and pigs and other cloven footed animals. The disease in pigs is mild and is important as being a potential danger for transmission to cattle. Transmission : Direct and indirect contact with infected animals. The virus can also be spread by aerosol, saliva, nasal discharge, blood, urine, faeces, semen, infected animal by-products, swill containing scraps of meat or bones and by biological products, particularly vaccines. Pigs can transmit the disease to cattle and other animals. Antemortem findings : 1. Incubation 3 – 15 days. Pigs that are fed food wastes contaminated with FMDV may show signs of infection in 1 – 3 days. 2. Snout (Fig. 116) and tongue lesions very common in pigs 3. Dullness and lack of appetite 4. Salivation and drooling 5. Detachment of the skin on a pig's foot (Fig. 117) 6. Shaking of feet and lameness due to leg lesions Some strains of FMD in swine do not show vesicles but show erosions. Judgement : Feverish animals with associated secondary bacterial infections call for total condemnation of the carcass. The meat of suspect animals may be conditionally approved after deboning, and condemnation of the head, feet, viscera and lymph nodes of the carcass. Such meat must be thoroughly cooked and could be used as canned meat. Differential diagnosis : Swine vesicular disease, vesicular stomatitis and vesicular exanthema in pigs can be differentiated from FMD only by laboratory testing. 125 Fig. 116: FMD. Vesicle on the snout in a pig. 126 Fig. 117: FMD Detachment of epithelium on the pig's foot. Hog cholera Hog cholera is a highly infectious viral disease of swine manifested by septicemia and generalized haemorrhage. It is noted in acute, subacute and chronic forms. 127 Transmission : Direct contact with infected pigs and ingestion of uncooked contaminated food wastes containing infected pork scraps. Antemortem findings : 1. Incubation 5 – 10 days 2. Morbidity 40 – 100 % 3. Mortality 0 – 100 %. Mortality varies with herd susceptibility, virus strain and age of animals. 4. Fever (40.6°C - 41.7°C) 5. Reddened areas of skin 6. Depression 7. Vomiting and constipation 8. Huddling and piling on top of each other 9. Incoordination with staggering gait 10. Tendency to sit like a dog 11. Goose stepping (Fig. 118) 12. Paddling 13. Infection of pregnant cows result in abortion Postmortem findings: 1. Tonsillar necrosis (Fig.119) 2. Splenic infarcts (Fig. 120) 3. Button ulcers in the large intestine and intestinal necrosis 4. Haemorrhage of the lymph nodes 5. Pneumonia in chronic infection 6. Petechial haemorrhage in the gall bladder, urinary bladder and kidneys (Fig.121); the latter is not present in acute hog cholera. Judgement : Carcass of an animal affected with hog cholera is condemned if kidney lesions are associated with lesions in the lymph nodes and other organs. If the meat appears normal after the organoleptic examination (appearance, taste and consistency), the carcass may be conditionally approved pending heat treatment or sterilization. Emergency slaughter of animals affected with hog cholera would require bacteriological examination of the meat in order to eliminate secondary pathogens, mainly Salmonellae. The animals in contact with hog cholera can be conditionally approved if heat treatment is carried out. Differential diagnosis : Erysipelas, septicemic conditions, pneumonia, streptococcosis and salt poisoning 128 Fig. 118: Hog cholera. Goose stepping. 129 Fig. 119: Hog cholera. Tonsillar necrosis. Fig. 120: Hog cholera. Splenic infarcts. 130